In various games and sports, players strike a ball by a stroke or a number of strokes using a striking implement to advance the ball from a ball striking location to a hole, pocket, receptacle or target area of a playing surface. For example, the objective in the game of billiards or pool is to project a cue ball directly, via other cue balls or boundary rails into pockets by using a striking implement known as a cue. Another example is the game of golf, wherein the objective is to advance a golf ball into a putting hole in the fewest number of strokes with the use of a striking implement commonly known as a golf club.
Conventionally, golf clubs have been designed for appearance, pendular properties and to dampen impact vibrations felt by a golfers' hand upon a golf ball strike. For example, U.S. Pat. Nos. 5,683,308, 5,928,090, 5,964,670, 6,007,431, and 6,641,489 are all configured to dampen impact vibrations upon ball strike.
Conventional putters are configured to absorb, not transmit, impact vibrations. Putter design has focused, primarily, on head shape, weight and balance properties, which help guide the eye and provide for a more stable stroke. Commonly, the head is of dense metallic form, and is suitably heavy to serve as the pendulum bob in a smooth and consistent stroke. The head typically has a resonance upon ball strike of several kHz or more. The shaft is thin walled steel expanded to a diameter of 5-15 mm with resonance around 100s of Hz. The attachment between the head and the shaft may be via epoxy or other adhesive or, in some cases, by threading or other mechanical connection. In any case, the connection, inherently or by design, provides very poor transfer of vibration from the head to the shaft. Often, a soft rubber grip is affixed to the shaft, further dampening what little vibration transfer may be present.
While dampening vibrations may be advantageous for full swing clubs, for putters and other partial swing clubs the vibrations caused by striking the ball can serve as useful feedback regarding the quality of stroke. In particular, the amount of shaft vibration can indicate to a player whether or not the desired “sweet spot” on the striking surface contacted the ball. Practically, golfers seek to feel what little vibration is transferred to their hands, by using a smaller club head than is optimal, and by removing any gloves before putting. It would be advantageous to amplify the vibrations caused by the impulse force of striking a ball, but few designs seek to do so. Those few have attempted to transmit vibrations to the hands of the golfer with minimal utility. For example, Rohrer (U.S. Pat. No. 7,140,973) discloses rigid vibration transmitting protrusions in intimate contact with the golfer's hands. Amato (U.S. Pat. No. 4,090,711) discloses a hollow shaft comprising a vibratory spring.